Where are startup communities, and how did they form?

In addition to Silicon Valley, vibrant startup communities have arisen in areas such as Los Angeles and Boulder, Colo., writes Eilene Zimmerman. "[I]n the past several years we've seen an incredible, accelerating shift in startup activity back to urban centers," urban studies professor Richard Florida said. Meanwhile, in cities such as Detroit and Las Vegas, entrepreneurs have spent millions of dollars to foster new startup communities.